Contact terminals of the type defined above are already known, these being able to be manufactured by cutting, folding, forming and possibly rolling of a sheet of metal strip much more economically than lathe-cut terminals. On the other hand, existing contacts made of cut and formed sheet metal have a number of drawbacks. If the contact blades initially bear against each other and require a high force to separate them, which is conducive to establishing a high contact pressure guaranteeing an electrical connection of good quality, the insertion force is high and there is a risk that introduction is difficult. This first drawback may become serious if a large number of contact terminals are provided in the same connector. If on the other hand the contact blades are initially separated, the pressure exerted by each contact blade may in some cases be insufficient to ensure good electrical connection.
One solution to this technical problem has been provided in Patent Application FR-A-2,621,180 which describes a female contact terminal which simultaneously guarantees satisfactory electrical connection and provides guidance of the male contact while it is being introduced. Thus each side wall has, at the front, a flap folded over inwards, retaining the flexurally prestressed contact blade in a position in which it is not in contact with the other contact blade.
At the present time, many contact terminals made of folded sheet metal furthermore run the risk of being crushed while they are being handled in production or at the premises of harness manufacturers. This is particularly the case with female electrical contact terminals in the form of a cage, but having a single wall, such as those described in U.S. Pat. No. 4,453,799 or EP-A-0,697,752, or else with those having contact blades which are not prestressed and which do not contribute to the stiffness of the cage, as described, for example, in Patent Application FR-A-2,627,020.
Single- or double-wall electrical terminals must moreover withstand any pull-out action or shearing action of the metal strip of which they are made. Thus, because of the cutting-out, forming and bending operations performed on these thin metal sheets, the intersections of the lines of cutting may shear and tear due to a lateral mechanical thrust being exerted on a wall or parallel thereto.
This risk is particularly high in the thinned regions, such as the transition region between the rear part for connection to an electrical wire and the front part formed by the cage, or else in the windows of the cage which are provided for fixing the terminal in plastic housings of the connectors receiving these terminals.
Finally, mention should be made of the risk of the forcible introduction of a male contact whose dimensions are greater than the internal dimensions of the cage, which contact would consequently apply a pressure, on the contact blades, greater than the pressure of the elastic deformation limit of the metal of which the contact blade is made, which would lead to eventual deterioration of the blade having then reached its plastic deformation limit.
These drawbacks become particularly important when, for economic reasons manufacturers, seeking solutions intended to reduce costs without impairing quality, envisage reducing the thickness of the metal strip of which the single electrically conducting metal sheet is made.